Part one of this series has got you interested in how you can build a more
powerful L-series engine. In this month’s article, I will try to clarify info
listed in the charts and explain which parts are best to use in the build-up.

There are many engine combinations that will get more power. Which combo you
choose depends on what your goals are. What kind of induction system you will
use are also things you will have to decide. For those with turbocharging in
mind, any of the choices that keep the compression ratio close to 8.0:1 will
allow more turbo boost and that will make more power. Generally speaking, lowering
the compression ratio in a turbo engine helps to reduce the threshold of detonation.
This is the point at which the fuel mixture begins to detonate or ping. You
can hear the dangerous knocking sound when you drive up hills under load and/or
have some low octane fuel in your tank. While under a load and at higher rpms,
this uncontrolled knocking can damage pistons and destroy your engine. So to
make power and do it safely, choosing the correct compression ratio for your
engine is important. For normally aspirated (non-turbo) engines, staying under
10.0:1 would be advisable for today’s Premium fuels. If you choose a ratio that
is in the mid 8.0:1 range, you might be able to still use the lower grades of
fuel. To keep throttle response up you would want to pick the highest ratio
that you can get away with. This will allow more power in a normally aspirated
configuration.

The various cylinder heads available for L-series engines each have their own
benefits. Perhaps some of the best choices are the N42 and the P90 cylinder
heads. The N42 head was used on the 75-76 and some early 77 280Zs and has the
square port exhaust configuration. The advantage of this head over the 240Z
heads is that it has larger intake and exhaust valves. This head has bolt holes
for either the carburetors or fuel injection manifolds. The P90 head was used
on the 81-82 280ZX Turbo and has the same features as the N42 but with a larger
volume combustion chamber. That larger volume will help to lower the compression
ratio necessary for a turbo engine. If you were to have the valves changed in
a 240Z head then those cylinder heads could be possible choices. With the plan
of creating a larger displacement engine, larger valves will allow more air
and fuel into the engine.

The best crankshaft choice is probably the one from the 1981-83 Maxima Diesel.
These Maximas had a diesel option (LD28 engine) and the crankshaft from these
engines is one of the keys to building a big Z engine. If you look at the charts
you see a chart that lists the pistons, rods and crank combos. Most of the combinations
listed use the LD28 crankshaft.

Which block is best for boring out to a larger size? 1975-81 non-turbo blocks
are the best. These have siamesed cylinders. What this means is that between
each of the cylinders, there is solid metal between them. The blocks to avoid
if you will bore big are the 1981-83 turbo blocks and the 1982-83 non-turbo
blocks. These blocks have an open casting area between the upper half of each
cylinder, which could collapse if bored too large. With overboring to 89-90mm,
you should pay the extra money to have the block sonic tested before the block
gets bored. This will determine if there was any sand casting shift or thin
areas (when the block was formed,) that could possibly lead to a collapsed cylinder
wall.

Connecting rod choices are either the L24 or the L28 depending on what combo
you pick. One thing to remember is that the early 240Z rods (up to 4/71) had
8mm rod bolts and the later 240Z rods (5/71-6/81) had 9mm rod bolts. You want
the rods with the 9mm bolts. You should buy and replace all the rod bolts and
nuts with new Nissan parts or use ARP brand bolts and nuts. The ARP company
makes racing hardware that is very good.

Piston choices like the other items, needs to be decided based on your desired
configuration. When buying your pistons, pay the extra for Nissan factory if
possible and definitely use Nissan factory rings. Custom forged pistons are
good if you plan to run high boost. Also use Nissan factory bearings if you
can. The quality of the factory parts is best and many race engines have used
these bearings. On the piston chart, where is says cut .5, this means having
the top of the piston milled or cut down .5mm. This keeps the piston top or
deck from sticking out of the top of the block.

The head gasket chart shows three choices. The HKS metal head gaskets are available
from Nissan Motorsports. Although a bit pricey, these are the only gaskets to
use when boring the block for larger than 88mm pistons.

In the next part of my series, I will discuss the preparation of the rotating
engine parts and the cylinder head work needed. I will pick some favorite engine
combinations and comment on induction choices and flywheel/clutch combinations.
If you have any questions at this point, feel free to e-mail me.

HEAD

VOL. C.C.

INT VALV.

EX VALV.

EXH. PORT

PROD. DATES

H/GASKET

HEIGHT

DIA.

C.C.

PART #

E31

42.4

42

33

square

10/69 - 7/71

L28 STD

1.25

88

7.60

11044-P7911

E88

44.7

42

33

square

9/71 - 7/72

HKS METAL

1

91

6.50

11044-91MM1

N33

47.8

42

33

square

8/72 - 7/73

HKS METAL

2

91

13.01

11044-91MM2

N33/P50

47.8

42

35

square

8/73 - 8/74

N42

44.6

44

35

square

9/74 - 7/77

PISTON

DIA MM.

PIN HEIGHT

DISH C.C.

PART #

N47

44.6

44

35

round

8/77 - 3/78

KA24E STD.cut .5

89

33.5

0

12010-40F10

P81

44.6

44

35

round

2/79 - 6/80

KA24E +1.00 cut
.5

90

33.5

0

12010-40F73

P79

53.6

44

35

round

7/80 -

Z24 STD. cut .5

89

33.5

13

12010-83W01

P90

53.6

44

35

square

12/80 - 7/82 TURB.

Z24 +1.00 cut .5

90

33.5

13

12010-83W03

P99

53.6

44

35

square

8/82 - TURB. HYD.

Z22S STD.

87

35

9.33

12010-06W11

Z22S +1.00

88

35

9.33

12010-06W13

PRACTICAL PISTON
/ ROD / CRANK COMBINATION

NO.

PISTON

ROD

CRANK

PIST/DECK +/-

CC VOL +/-

SIZE C.C.s

CRANK

STROKE

PART #

#1

KA24E STD.cut .5

L24

LD28

0.13

-0.8

3098

L28

79

12201-P3000SV

#2

KA24E +1.00 cut .5

L24

LD28

0.13

-0.83

3168

LD28

83

12201-V0790

#3

Z24 STD. cut .5

L24

LD28

0.13

-0.8

3098

#4

Z24 +1.00 cut .5

L24

LD28

0.13

-0.83

3168

BLOCK

HEIGHT

#5

Z22S STD.

L28

LD28

-1.02

6.06

2960

L28

207.87

#6

Z22S +1.00

L28

LD28

-1.02

6.2

3028

#7

KA24E STD

L24

L28

-1.37

8.5

2949

R0D

LENGTH

PART #

#8

KA24E +1.00

L24

L28

-1.37

8.71

3015

L24

133

12100-N0102

L28

130.35

12100-A8703

COMPRESSION RATIO
USING HKS 1.MM HEAD GASKET FOR ABOVE COMBINATIONS

HEAD

#1

#2

#3

#4

#5

#6

#7

#8

E31

11.73

11.98

9.45

9.65

8.67

8.83

9.56

9.72

E88

11.24

11.48

9.14

9.33

8.41

8.56

9.23

9.39

N33

10.65

10.87

8.76

8.94

8.08

8.23

8.83

8.97

N33/P50

10.65

10.87

8.76

8.94

8.08

8.23

8.83

8.97

N42

11.26

11.50

9.16

9.34

8.42

8.57

9.25

9.40

N47

11.26

11.50

9.16

9.34

8.42

8.57

9.25

9.40

P81

11.26

11.50

9.16

9.34

8.42

8.57

9.25

9.40

P79

9.71

9.91

8.14

8.31

7.53

7.67

8.16

8.30

P90

9.71

9.91

8.14

8.31

7.53

7.67

8.16

8.30

P99

9.71

9.91

8.14

8.31

7.53

7.67

8.16

8.30

Courtesy of Jim Wolf Technology Rod width at small end must be reduced to fit KA24 and Z24 pistons.
‘91+ 240SX pistons can be substituted for Z24 pistons.